A synchromesh type transmission mechanism is configured such that, when a synchronizer ring is pressurized by a key based on an axial movement of a sleeve spline-coupled to a hub, the speeds of the hub, the sleeve, and a clutch gear are synchronized by a frictional force generated between the synchronizer ring and a clutch cone of the clutch gear. Accordingly, the sleeve is coupled to the clutch gear, and consequently a driving force is transferred between the hub and a transmission gear integrally connected to the clutch gear. However, according to the related art, it is difficult to ensure sufficient durability of each component of the transmission mechanism as described above should.
The above description in this background section is merely for improving understanding of the background of the present disclosure, and should not be taken as an acknowledgement indicating that the information forms a prior art that is already known to a person skilled in the art.